Dehydration of potatoes by use of brine



United States Patent 2,797,166 DEHYDRATION OF POTATOES BY USE OF BRINEJames Siciliano, Woodbury, N. J., and Edward G. Heisler,

Plymouth Meeting, and Robert H. Treadway, Philadelphia, Pa., assignorsto the United States of America as represented by the Secretary ofAgriculture No Drawing. Application January 26, 1954, Serial No. 406,367

2 Claims. (Cl. 99-207) (Granted under Title 35, U. S. Code (1952), see.266) A non-exclusive, irrevocable, royalty-free license in the inventionherein described, for all governmental purposes, throughout the world,with power to grant sublicenses for such purposes, is hereby granted tothe Government of the United States of America.

This invention relates to the partial dehydration of raw potatoes bysoaking them in a salt solution.

Raw potatoes contain about 80 percent of water, the presence of whichmakes handling and shipping expensive and favors decomposition instorage. Completely dehydrated potatoes are stable in storage and lightin weight. However, no completely satisfactory method of dehydration hasever been found, despite extensive research. All the methods known tothe prior art are too expensive or they damage the product so that therehydrated potato is of inferior quality.

Salt (sodium chloride) and salt solutions (brine) have been used towithdraw water from many substances to yield a partially dehydratedproduct which could then be used as such or could be further dehydratedby other methods.

Theory predicts, and prior art experience teaches, that in the use ofbrine to extract water from a plant tissue, such as potatoes, the moreconcentrated the brine and the longer the soaking period the more wateris removed from the tissue.

The object of this invention is to provide an improved process for thepartial dehydration of raw potatoes by soaking in brine.

According to the invention, the mam'mum amount of water is removed fromthe raw potatoes by soaking the potatoes in a dilute brine for anoptimum period. This is effected by immersing the raw potato, thesmallest dimension of which does not exceed about 4 inch, in aqueousbrine of at least about 2% concentration, preferably about 3%concentration, for at least about 2 hours, preferably for about from 5to 7 hours, at a temperature up to about 35 C., preferably from about 25C. to 35 C., to remove about from 21% to 28% of the moisture from thepotato. The use of highly concentrated brine, even to the point ofsaturation, or the use of periods of time exceeding about 7 hours resultin the removal of a lower percentage of the water present in the potato.

To determine the eifect of varying the concentration of salt on themaximum amount of water removed and the time required to reach thatmaximum, a series of experiments were run in which raw potato slices 4inch thick were soaked in brine at room temperature (25 (3.). Theresults are shown in Table I.

r 2,797,166 Patented June 25, 1957.

Max. Water Removed.

Percent of Total Cone. of Brine, percent Tim Hrs.

From the above data it may be seen that the maximum water removed wasefiected by use of 3 percent brine, and 7 hours was required to reachthat maximum. In these experiments, the amount of water removed in-.creased with time of soaking until the maximum was reached in the timeshown. Further soaking resulted not merely in cessation of dehydrationbut in more or less rehydration.

While the use of 3 percent brine resulted in maximum dehydration, itshould be noticed that use of 4 or 5 percent brine achieved almost asmuch dehydration and did so in considerably less time. Because of thissaving of time, and because the brine becomes diluted with use, wegenerally prefer to put the brine into the process at about 5 percentconcentration and withdraw it at about 3 percent. Alternatively, we mayadd salt to the brine as needed to maintain it at substantially aconstant concentration.

It is readily apparent that the process may be operated in a batchwise,semi-continuous or continuous manner without departing from the basicprinciple of the invention.

It has been found that the rate of dehydration is alfected by changes intemperature. Increasing the temperature increases the rate ofdehydration until about 35 C. is reached. Above this point the potatostarch granules begin to swell, thus impeding the dehydration. Thiseffect is illustrated by the data in'Table II. In these experiments /4inch slices of potato were immersed in 3 percent brine until maximumdehydration had been achieved.

Table II.Efiect of temperature on dehydration Max. Water Temp., 0.Removed, Time,

Percent 0! Hrs.

Total From these data it can be seen that there is little difference inthe maximum water removed in the range 25-35 but at higher temperaturesthere is a sharp drop in water removed. However, the rate of waterremoval increases with temperature; hence it is advantageous to operateat a temperature up to about 35 in order to increase through-put withoutamount of water removed.

The physical form of the potatoes is not important except that verythick sections should be avoided because of their slow rate ofdehydration. Thus, when sliced potatoes are dehydrated by use of 3percent brine at 25 C. the time required for maximum water removalvaries with the thickness of the slices. Three-quarter inch slicesrequired 20 hours, inch slices required 7 hours, while 0.04 inch slicesrequired hours. From these data it;-is' apparentthatzlittle savingjintime can be expected from :use;of;sliees:less than A. inchin zthickness.On .the other.hand,.whole.potatoes 01 very thickslices require an.excessi-ve'time for dehydration. As a practical matter, we generallyprefer dieed=or sliced potato having the smallest dimension about A inchor less. Potatoes that .are..to .be. friedas chips, .juliennestrips, orfrench-fries should be cut into the proper form for frying before beingsoaked-in-brine.- -Partial-dehydration -of such raw :potatoes by' ourprocess jishighly advantageous in that less time is required-for-frying-'andin the case 'of chips the product is less subject to crumbling inpackaging and handling than are-conventional'chips.- The process of thisinvention is particularly useful in the manufacture of potato granules,a cooked, dehydrated potato product in which the cells are mostlyintactand which is readily reconstituted .to mashed potatoes for table use. vIn the conventional processes for making granules it is necessary in thedehydration step to recycle a large seriously reducing the part of theproduct by mixing with the fresh mashed potato in order to get amaterial that will go through the drying step without excessive lumping.By first subjecting the raw potato to our partial dehydration processthe moisture content can be reduced so far that the proportion of dryproduct required for recycling can be drastically reduced, thus greatlyincreasing the capacity of the drier as well as improving the quality ofthe product.

We claim:

1. A process for partially dehydrating raw potato comprising immersingraw potato, the smallest dimension of which does not exceed'about inch,in aqueous brine of at least about 2% concentration for at least about2,

hours at a temperature up to about C. vto remove about from 21% to 28%.of the moisturetherefrom.

2. A process for partially dehydrating raww 'potato comprising immersingraw potato, the smallest dimension of which does not exceed aboutA'inch, inaqueous brine of about 3% concentration for about from 5 to 7hours at a temperature of about from 25 C. to 35 C. to remove about from25% to 28% ofthe moisture therefrom.

1,259,635 2,190,063' Gano Feb. 13, 1940 2,681,285 'Hendel et a1. June15, 1954

1. A PROCESS FOR PARTIALLY DEHYDRATING RAW POTATO COMPRISING IMMERSING RAW POTATO, THE SMALLEST DIMENSION OF WHICH DOES NOT EXCEED ABOUT 1/4 INCH, IN AQUEOUS BRINE OF AT LEAST ABOUT 2% CONCENTRATION FOR AT LEAST ABOUT 2 HOURS AT A TEMEPERATURE UP TO ABOUT 35*C. TO REMOVE ABOUT FROM 21% TO 28% OF THE MOISTURE THEREFROM. 